1. Technical Field of the Invention
The present invention relates generally to coolant systems, and more particularly, to a pressurized air powered turbine coolant system.
2. Description of Related Art
Aircraft typically employ an air cycle Environmental Control System (xe2x80x9cECSxe2x80x9d), to cool, filter, pressurize and otherwise condition enclosures such as an aircraft cabin and cockpit. An air cycle ECS typically operates on a flow of bleed air taken from an intermediate or high pressure stage within a jet engine having multi-compression stages or from an Auxiliary Power Unit (xe2x80x9cAPUxe2x80x9d) that is a separate turbine engine, not used for propulsion, to power the ECS. Since compressed ambient air or engine bleed air is readily available it is a convenient source of power for an airborne ECS. In most systems the engine bleed air is passed through a heat exchanger (HX), cooled by a ram air or fan driven arrangement thereby lowering its temperature. To further lower the temperature and pressure of the engine bleed air to usable levels, the bleed air is subsequently expanded in a refrigeration turbine. On a typical simple cycle system the turbine also drives the ram air fan. From the turbine, cold air is routed through the aircraft for various functions (cockpit cooling/pressurization, forced air avionics cooling, etc.). After this air has been used it is generally not reclaimed for any other use and it is discharged overboard.
The use of cooled air for the cooling requirements of current avionics is inefficient and/or impractical for high powered/liquid cooled equipment, particularly for performance sensitive aircraft such as military fighters and, more particularly for avionic retrofits. For example, an air supply duct will typically require 10 to 15 times the volume of a pair of coolant lines to cool the same heat load.
Additionally, ram air configurations and fan driven configurations both reduce the efficiency or performance of the aircraft. For, example, ram air configurations include air ducts that must run from the outer side of the aircraft, to the associated HX, which occupies additional space within the aircraft. This limitation not only consumes valuable interior space for new designs, it also makes retrofitting existing aircraft difficult or impossible. Further, an associated ram air scoop is typically exposed on an outside surface which can increase drag and increase the radar-cross-section of military aircraft. Fan driven and other types of auxiliary power devices require additional sources of power for drive. This additional work load further reduces fuel consumption efficiency and may require more equipment on board.
Vapor Cycle Systems (xe2x80x9cVCSxe2x80x9d) have also been used to provide cooling for the aircraft avionics without the excessive use of engine bleed air. VCS typically use a supply of power other than bleed air to cool avionics (electrical power, direct engine shaft power, etc). The electronically driven compressor is typically supplied with electric power from shaft driven generators. However, since electronic power or shaft power must be supplied by the aircraft engine to run the compressor, the efficiency gained by using less bleed air is lost by the power requirements of the compressor, particularly for aircraft which rely upon speed and power such as is the case with military aircraft.
Many of the above-described problems are exacerbated when avionics are added to existing aircraft in which the retrofit aircraft must supply both additional electric power and cooling to support the new avionics. The traditional approach to solving the problem of adding more cooling and electrical power to an existing aircraft usually involves changes to multiple systems. Installing a larger generator to get more electrical power can affect the Aircraft Mechanical Accessory Drive (xe2x80x9cAMADxe2x80x9d) and its cooling requirements due to the higher power takeoff requirements. Adjacent systems (such as typically hydraulic pumps, emergency generators and engine starting drives), connection routing, and structure are also affected. Adding cooling capacity typically requires an increase in aircraft volume, typically involving movement of existing equipment to create the space in the airplane to install a larger ECS. A larger ECS usually requires significant changes to bleed air routing, such as larger ducts, and structural changes as well as additional ram air. The ECS bay is similar to the AMAD bay in that the available volume is fully utilized to install the highest capacity system possible during initial design of the aircraft. In order to increase available cooling the ECS would need to grow beyond its current volume. It is impractical to relocate ECS components to other bays because of the large connecting ducts. Therefore, moving avionics from an adjacent bay is a more viable approach. However, this involves re-routing many connecting harnesses that may ultimately affect other harnesses, structural penetrations, etc. which adds to the overall cost of the change. The equipment that was displaced requires new routing, racks, and structure. Removing fuel is generally considered a poor solution because it affects range and endurance.
When all of the costs associated with the above-mentioned changes are summarized, it is usually determined to be prohibitively expensive. In an industry faced with increasing fuel costs and heightened environmental concerns, considerable effort is made to reduce weight and energy requirements without sacrificing overall system performance. Many times the client must decide if it is better to buy new aircraft with the right capabilities or spend a lot of money on updating a used aircraft or compromise the capability of the new systems to live within the existing power and cooling constraints.
The present invention achieves technical advantages as an apparatus, system and method for providing chilled coolant and electrical power. Air is extracted from a pressurized air source. An air-to-air heat exchanger receives and cools the extracted pressurized air. Further, an expansion turbine receives at least a portion of the cooled pressurized air from an output of the air-to-air heat exchanger and is configured to expand the cooled pressurized air into chilled air while extracting work. An air-to-coolant heat exchanger receives the chilled air from the expansion turbine which is used to chill refrigerant coolant in a heat transfer relationship. The air-to-air heat exchanger also receives the chilled air reclaimed from the air-to-coolant heat exchanger, subsequent to chilling the refrigerant coolant, where the extracted pressurized air is cooled with the reclaimed chilled air. In one embodiment, the extracted work is used to drive a generator to supply electricity to a distribution system.